The present invention relates to airbags and the sensors used in determining the conditions under which an airbag is deployed.
The deployment of airbags within an automobile to protect the driver or passenger during a crash has continuously become more sophisticated. Multiple airbags or airbags with adjustable inflation parameters have been used in combination with the sensors that determine the presence, the weight, and the position of the occupant opposite an airbag. By knowing the occupant""s weight and position, algorithms can be used to tailor the deployment of an airbag either in time or intensity to the particular circumstances of a particular automobile crash and a particular occupant and that occupant""s position. Generally, such sensors are designed to increase the overall benefit derived from the presence of an airbag within an automobile. There is thus considerable incentive to add more sensors combined with more complicated deployment algorithms. On the other hand, each additional sensor adds cost and can theoretically increase the cost of maintenance by increasing the number of wires and sensors, which may need to be replaced or maintained.
The manufacturers of automobiles have always been sensitive to the fact that each part, though having only a small cost in itself, when multiplied by sometimes over a million cars of a particular type sold, can constitute a significant total cost. Hence, substantial cost savings can be realized if parts can be eliminated without decreasing functionality.
One area which it has been found desirable to monitor is the position of a seat within an automobile. The seat position gives an indication of the size of the occupant and determines, at least in part, the occupant""s position relative to one or more airbags which could be deployed. Thus the position of the seat, whether fully retracted, fully extended, or positioned somewhere in between, is supplied to a controller which uses the information in deciding how and when to deploy one or more airbags. A number of different types of sensors can be used, including those, which supply a continuous varying output depending on seat position, and those which provide discrete output indicating one or more discrete seat locations. The discrete sensors provide the possibility of greater reliability, both because such sensors tend to be inherently reliable, and because the information, which must be transmitted to the airbag deployment logic controller consists of a single logic state. Furthermore, such sensors may often be cheaper than a more sophisticated sensor capable of providing a continuously varying output with seat position.
However, the use of discrete sensors presents the problem that more sensors are needed for more precise determination of seat position. What is needed is a seat positioning system, which reduces cost and increases reliability by reducing the number of discrete sensors without decreasing the precision of seat position determination.
The seat positioning system of this invention employs a ferromagnetic vane mounted to an automobile seat on the portion of the seat track which moves, and a plurality of sensors spaced along the nonmoving seat track. The ferromagnetic vane is chosen so that it can activate one sensor if positioned over that sensor, or two sensors if it is positioned over two sensors, or three sensors if positioned over three sensors. The physical arrangement of the ferromagnetic vane and the sensors is combined with a logic within the deployment controller which determines the seat position as being either over a particular sensor when one sensor is activated, or between two sensors when both sensors are activated. In this way the number of sensors required for a particular degree of seat position resolution may be reduced. Two sensors can be used to detect four seat positions, three sensors can be used to detect six seat positions, four sensors can be used to detect eight seat positions, etc. In general, the number of seat positions that can be detected is equal to two times the number of sensors. This substantial reduction in the number of sensors required is accomplished by the addition of programming logic to the controller which adds zero incremental cost to an automobile, thus providing a cost savings without a decrease in performance. In an alternative arrangement the sensors are mounted on a moving seat and a ferromagnetic vane is mounted beneath the seat so that the vane operates one or two of the seat mounted sensors at a time.
It is a feature of the present invention to provide automobile vehicle seat positioning information at lower cost.
It is another feature of the present invention to provide an automobile car seat positioning detecting system with reduced cost without reduced performance.
It is a further feature of the present invention to provide an automobile car seat positioning detecting system which substitutes controller logic for sensing hardware.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.